/*
 Copyright  2002-2007 MySQL AB, 2008 Sun Microsystems
 All rights reserved. Use is subject to license terms.

  The MySQL Connector/J is licensed under the terms of the GPL,
  like most MySQL Connectors. There are special exceptions to the
  terms and conditions of the GPL as it is applied to this software,
  see the FLOSS License Exception available on mysql.com.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; version 2 of the
  License.

  This program is distributed in the hope that it will be useful,  
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  02110-1301 USA



 */
package com.mysql.jdbc;

import java.sql.SQLException;

/**
 * An exception to represent communications errors with the database.
 * 
 * Attempts to provide 'friendler' error messages to end-users, including last
 * time a packet was sent to the database, what the client-timeout is set to,
 * and whether the idle time has been exceeded.
 * 
 * @author Mark Matthews
 * 
 * @version $Id: CommunicationsException.java,v 1.1.2.1 2005/05/13 18:58:37
 *          mmatthews Exp $
 */
public class CommunicationsException extends SQLException implements StreamingNotifiable {

	
	private String exceptionMessage = null;

	private boolean streamingResultSetInPlay = false;
	
	private ConnectionImpl conn;
	private long lastPacketSentTimeMs;
	private long lastPacketReceivedTimeMs;
	private Exception underlyingException;

	public CommunicationsException(ConnectionImpl conn, long lastPacketSentTimeMs,
			long lastPacketReceivedTimeMs, Exception underlyingException) {
		
		// store this information for later generation of message
		this.conn = conn;
		this.lastPacketReceivedTimeMs = lastPacketReceivedTimeMs;
		this.lastPacketSentTimeMs = lastPacketSentTimeMs;
		this.underlyingException = underlyingException;
		
		if (underlyingException != null) {
			initCause(underlyingException);
		}
	}

	

	/*
	 * (non-Javadoc)
	 * 
	 * @see java.lang.Throwable#getMessage()
	 */
	public String getMessage() {
		// Get the message at last possible moment, but cache it 
		// and drop references to conn, underlyingException
		if(this.exceptionMessage == null){
			this.exceptionMessage = SQLError.createLinkFailureMessageBasedOnHeuristics(this.conn,
					this.lastPacketSentTimeMs, this.lastPacketReceivedTimeMs, this.underlyingException, 
					this.streamingResultSetInPlay);
			this.conn = null;
			this.underlyingException = null;
		}
		return this.exceptionMessage;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see java.sql.SQLException#getSQLState()
	 */
	public String getSQLState() {
		return SQLError.SQL_STATE_COMMUNICATION_LINK_FAILURE;
	}

	/* (non-Javadoc)
	 * @see com.mysql.jdbc.StreamingNotifiable#setWasStreamingResults()
	 */
	public void setWasStreamingResults() {
		this.streamingResultSetInPlay = true;
	}

}
